This invention relates in general to a polymeric matrix and in particular to a polymeric matrix for use on a receptor medium utilized in thermal transfer recording.
One of the more important non-impact printing technologies is the thermal transfer printing process. It has several advantages over traditional mechanical impact printing, such as high resolution, low noise level and high speed. However, a thermal transfer printer requires a printing medium tailored for its specific process.
The thermal transfer process is complex with the final imaging results dependent not only on the receptor sheet, but also the donor sheet and printer. Thus the ink composition and the printer design play a role in the quality of the imaged product. This invention teaches how generally to obtain good performance.
The thermal transfer printing process involves three components: a thermal print head, a thermal transfer ribbon consisting of a foundation and a heat-sensitive ink donor layer applied thereon, and an ink receptor sheet. The inked side of the thermal transfer ribbon is placed in contact with the ink receptor sheet, and heat from the thermal print head is applied to the backside of the thermal transfer ribbon. The heat is conducted through the plastic or paper ribbon and locally raises the ink (colorant and carrier matrix) temperature above its softening point. The softened ink partially wets the ink receptor sheet, transfers to it and re-solidifies.
It is known to those skilled in the art to choose compatible materials in the donor and receptor components. Compatibility is often discussed in terms of solubility parameters (Handbook of Adhesives, 2nd Edition, I. Skeist, published by van Nostrand, 1977).
A wide variety of different types of thermal transfer ink receptor media have been proposed heretofore. For example, Japanese Patent 63-237,989 describes an ink-receptor sheet containing two aromatic polyamide layers having different roughness; Japanese Patent 64-072,662 describes a two-layer ink-receptor sheet comprising a metal oxide layer and an adhesion layer; Japanese Patent 64-072,663 describes an ink-receptor sheet consisting of a sponge urethane or a foam styrene; and Japanese Patent 63-69,685 describes an ink-receptor sheet containing an aluminum silicate and a polymer binder. Some patents describe wax-containing and wax compatible ink receptor layers. Examples of such patents include Japanese Patents 59-229,394, 60-49,997, 60-174,695, 60-154,096, 64-072,664, 63-237,988, 63-170,087 and European Patent Publication 228,835 (U.S. Pat. No. 4,686,549). Some patents describe ink receptor layers coated on an opaque substrate such as paper. Examples of such patents include Japanese Patents 60-49,997, 60-54,891, 59-229,394, 63-17,079, 61-139,487, 60-56,594, 63-237,986, 62-173,293, 63-77,780, and 59-194,888.
Despite the substantial prior art, none have achieved the image quality required by the end user. Density is frequently low and half tones are poorly rendered, resulting in inadequate tonal quality.
We have now devised a polymeric matrix which is particularly suitable as an ink receptor medium for thermal transfer recording.